Mount Prospect, Illinois 7 Day Weather Forecast

Wx Forecast - Wx Discussion - Wx Aviation

156
FXUS63 KLOT 031117
AFDLOT

Area Forecast Discussion
National Weather Service Chicago/Romeoville, IL
617 AM CDT Wed Jun 3 2026

.KEY MESSAGES...

- Unseasonably warm (and dry) conditions today (away from the
  lake) and then area-wide Thursday.

- Potential for an increased fire danger on Thursday due to
  warm, dry, and breezy conditions.

- Periodic shower and thunderstorm chances return Friday into
  Saturday and potentially into early next week.

&&

.DISCUSSION...
Issued at 127 AM CDT Wed Jun 3 2026

Surface high pressure will remain in control of our sensible
weather today as it builds eastward across lower Michigan.
Temperatures will get a several degree boost, settling largely
in the mid 80s, and lake cooling will be confined to immediate
shoreline locales. Given the surface high location, initially
offshore southeasterly winds this morning across Indiana
lakeside locales may allow these areas to warm quickly into the
lower 80s prior to the afternoon lake breeze passage. With a
lingering layer of fairly dry air aloft, have continued to drop
afternoon dewpoints in anticipation of another day of deep
diurnal mixing which yields widespread afternoon RH values
either side of 20 percent (locally into the teens) away from
the immediate lake influence.

Broad southwesterly flow will establish across the area on
Thursday. No precipitation is expected through the daytime
hours, but increasing high cloud cover will occur through the
afternoon. Southwesterly breezes, occasionally gusting around 25
mph, combined with afternoon RH values dropping to around 25 to
30 percent, and fairly parched conditions with the lack of
wetting rainfall may lead to a somewhat elevated fire danger.
It`s also possible that dewpoints/RH values mix out further than
currently indicated.

As previously expansive, high amplitude blocking breaks down
through the end of the week, a series of shortwaves and
convectively augmented disturbances will bring increasing
chances for showers and some storms to the area, mainly Friday
and into Saturday.

Generally broad quasi-zonal upper level flow will allow an
initial lead wave ahead of a more robust/compact upstream
shortwave to drift into the region towards Friday morning. While
surface dewpoints will rise in the mid and upper 60s, 500 mb
temperatures only near -10 C, associated meager mid-level lapse
rates, and the potential for increased morning cloud
cover/showers all look to generally temper instability values
locally. Showers and isolated to perhaps widely scattered
thunderstorms will be possible through the day on Friday,
although it`s still unclear just how widespread precipitation
will be given the modest nature of large scale forcing in place
during the day.

The aforementioned more robust shortwave is forecast to approach
and then move across the general vicinity late Friday night and
into Saturday. Noting lots of spread across the guidance suite
regarding the handling of not only the parent shortwave but also
the placement and magnitude of low-level boundaries. This
ranges from a well-defined stalled front in our south (NAM) to
a notably more diffuse boundary in the latest GFS. The
deterministic 00z ECMWF is somewhere in between. With a
seasonably moist airmass in place (PWATs north of 150% of
normal) and the arrival of more coherent large scale forcing,
additional showers and thunderstorms will be possible during
this timeframe.

This shortwave looks like it`ll track east of the region through
Saturday afternoon. While large scale forcing will diminish with
time, an incoming weak front/lake breeze may serve as a focus
for some additional shower and thunderstorms. On Sunday and
Monday, the low-level theta-e axis is forecast to either push
entirely south of the region, or just clip our far
west/southern locales. NBM PoPs during this timeframe have
trended lower which is appropriate given the latest model
trends.

Through the middle of next week, the trend in the medium range
suite has been towards the development of another omega
blocking pattern across the CONUS. It`s unclear if the primary
ridge axis will set up close enough to allow surface high
pressure to build back over the region or if a lingering moist
plume will slosh back into the area with renewed precipitation
chances.

Carlaw

&&

.AVIATION /12Z TAFS THROUGH 18Z THURSDAY/...
Issued at 617 AM CDT Wed Jun 3 2026

There are no key concerns for the 12Z TAF period.

Light and variable winds early this morning will open up to SE
at largely less than 10 kt by mid morning. At GYY, a lake breeze
will flip winds to NE in the afternoon before veering again in
the evening. Direction turns to SSW around 06Z tonight and
speeds will build into the teens kts by mid morning Thursday.
VFR can be expected through the period.

Doom

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...None.
IN...None.
LM...None.

&&

$$

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